Waterproofing of roofs of commercial buildings is regularly achieved by applying polyurethane foam to the roof by spraying, followed by applying a sealer or protective coating. While the polyurethane foam material used for such projects has been refined over many years of development, the application of such materials on roof tops has continued to present the problems caused by overspray.
In applying such materials under conventional practices, a controlled mixture of components is produced at the site and is sprayed, under pressure, onto the roof top, using a manually controlled, handheld applicator. Atomized particles of polyurethane are emitted and can be carried by wind or any air current from the roof top and deposited to the surrounding area. Generally, such polyurethane foam does not set up until it contacts the surface on which it is deposited. Thus, in most cases, any overspray of material will result in damage occasioned by deposit onto the surrounding area. For example, overspray resulting from the application of polyurethane foam on a commercial structure in a built up area, can expose hundreds if not thousands, of automobiles, as well as equipment and other buildings to the overspray. Such exposure can result in large damage claims.
As a result, spraying of polyurethane foam on commercial buildings is greatly restricted as a result of wind conditions and postponing the application of polyurethane foam is often required because of high wind conditions which cause overspray, even though the other conditions for spraying are ideal and equipment and manpower available. As a result of the possibility of damage which can result from overspray, an operator must balance such liability against the loss which is occasioned by excessive down time. Further, liability and loss as a result of overspray has had a dramatic impact on the cost of liability insurance and the amount of such insurance which a contractor can carry. Excessive liability claims may even result in the disqualification for insurance coverage.
As a result of such potential damage which can be caused from overspray of polyurethane foam, as well as other materials which are used on roof tops of commercial or other buildings, a need has existed for some time for a method and structure which would eliminate such problem. In the past, attempts have been made to erect wind screens which would act as a barrier between wind and the polyurethane foam as it is sprayed. However, such wind screens have proved to be ineffective in that they have been incapable of preventing movement of wind either around or over the screen to then affect the polyurethane spray. Likewise, shifting of wind direction and controlling wind gusts from various directions have rendered such wind screens ineffective.
The development of a successful enclosure in which the spraying can be conducted, has also not been successfully achieved. First, because such structure must be positioned at the top of a building structure, its construction, including weight and assembly, has been a hindrance to developing a successful product. Further, any barrier to the polyurethane spray must provide proper ventilation and be stable in operation. Further, such a device would have to be highly maneuverable to be capable of traversing all areas on a roof top, even those which have protrusions therethrough and are of irregular shape.
U.S. Pat. No. 4,315,458, to Raymond M. Hudson, entitled "Ventilated Wind-Diverter Shed for Man-Spraying of Polyurethane Foam From Within onto Roofs" discloses a motorized shed which travels on a rail to traverse a roof top for spraying of polyurethane foam from within. The structure is primarily devised to provide a lower wind diverter section with a ventilated upper portion. The equipment requires movement on a rail which of course severely restricts use of the device. Further, no specific structure for the shed is shown, only a diagrammatic view being depicted in the patent.